Just what we don’t need: an especially active hurricane season

Evidently the risk of blue tarps on people’s houses for long periods of time as they wait to collect from an insolvent Texas Windstorm Insurance Association following a moderate or severe tropical cyclone this summer or next has not been enough to motivate the Texas legislature to do anything serious about the problem during its regular session. Here’s one more piece of evidence, the new 2013 Atlantic Hurricane Forecast, suggesting that this failure to act leaves the Texas coast in grave danger and the rest of Texas at serious risk.  It strengthens calls for Governor Rick Perry to add windstorm reform to the agenda for a special session.

The National Oceanic and Atmospheric Administration’s Climate Prediction Center today joined other scientists (here and here) in predicting a worse than average hurricane season. They write:

This combination of climate factors historically produces above-normal Atlantic hurricane seasons. The 2013 hurricane season could see activity comparable to some of the very active seasons since 1995. Based on the current and expected conditions, combined with model forecasts, we estimate a 70% probability for each of the following ranges of activity during 2013:

  • 13-20 Named Storms
  • 7-11 Hurricanes
  • 3-6 Major Hurricanes
  • Accumulated Cyclone Energy (ACE) range of 120%-205%

The seasonal activity is expected to fall within these ranges in 70% of seasons with similar climate conditions and uncertainties to those expected this year. These ranges do not represent the total possible ranges of activity seen in past similar years.

Note that the expected ranges are centered well above the official NHC 1981-2010 seasonal averages of 12 named storms, 6 hurricanes, and 3 major hurricanes.

If, by the way, we assume a 50% higher number of tropical storms this year than average, the risk of TWIA becoming insolvent if it has $1 billion (after limited success selling post-event bonds) with which to pay claims goes from roughly 7% this year to roughly 10% this year. If we assume, as the most optimistic people do, that TWIA might have access to $3.5 billion (after successful post-event bond sales and some reinsurance), the risk of insolvency goes from roughly 2% to roughly 3%. All of these numbers are too high for comfort.

The only comfort one can obtain from this forecast of the 2013 Atlantic hurricane season is that it could, of course, be wrong.  Hurricane predictions, particular this far in advance, are not the most reliable forecasts out there.  NOAA has taken this into account, however, by saying that there is only a 70% chance that its forecast will be right.  Still, a 70% (or, technically greater) chance that we will have a greater than average number of Atlantic hurricanes this year, when TWIA, even with the most cheery assumptions, is still underfunded, should make one’s stomach churn as if in sympathy with the future waters of the Gulf.

My thanks to Houston Chronicle blogger extraordinaire, SciGuy Eric Berger, for bringing this news to my attention.



The curious case of Corpus Christi

Today’s Corpus Christi Caller has an interesting article that purports to show a special immunity of the Corpus Christi area to hurricane risk, which is said to be no more than that facing New York City. The article is based on a report from NOAA published since 2010 and apparently brought to the recent attention of Todd Hunter, Corpus Christi’s state representative. It’s based on data from 1887 forwards that attempts to calibrate the comparative risk of landfall both within Texas and throughout the Gulf and Eastern Seaboard.

Here’s the key picture which, though not shown in the report, appears to underlie the article’s conclusions and quotations.

Return periods of Atlantic hurricanes

Return periods of Atlantic hurricanes by county

See the blue 19 next to Corpus Christi and the blue 20 next to New York City. This is supposed to show that the risk of hurricanes in those two regions are similar: one every 19 or 20 years a hurricane will strike within 50 miles. And see the orange 9s next to Galveston and Brazoria counties. That is supposed to show that the risk of hurricanes in those two regions are greater, once every 9 years.

The evidence gets a bit more complicated, however, if one looks at the next picture in the NOAA document, one not mentioned in the Caller article. It shows the history of major hurricanes based on historic evidence from 1887 to 2010. Although the coastal bend (33-40 years) still comes out better than the east Texas coast (25-26 years), the ratio isn’t as great as for all hurricanes. Moreover, the comparison with New York City now fails. The Big Apple gets hit only once every 68 years.

Major hurricane return periods

Return period for major Atlantic hurricanes by county

So, what are we to make of all this? I would say not too much. What the NOAA report lacks is any notion of statistical significance that would make it particularly useful in drawing fine grained distinctions between areas of the Texas coast. It might just be that what the pictures show is significantly good and bad luck. Drawn from a sample of just 130 years or so, one might expect to see distributions of return periods that varied from county to county. Perhaps some trends might be observable, such as greater strike frequency in Florida than Texas, but what the report lacks is a “p-value,” the probability that one would see variations in the data as large as those exhibited in the graphics simply as a matter of chance. I’m not faulting NOAA for this; it would be very hard to develop such a statistic and it was purporting to capture historic evidence only. Moreover, our climate is dynamic. Storm tracks and storm frequency can change as a result of global weather phenomenon. Thus, while one should not ignore historic data, you have to be very careful about projecting it into the future or using it to make highly specific projections.

So, should the report be ignored? No. Perhaps curious atmospheric features (jet stream placement) and geographic features such as the placement of Cuba indeed give Corpus Christi a little shield. And if Corpus Christi wants to argue on that basis for lower rates for southwest coastal Texas and higher rates for the eastern Texas coast, I wouldn’t be mightily opposed. Somehow, however, I don’t think that’s where coastal Texas wants to go in the upcoming legislative session. Recognition of large differences based on geography in catastrophe risk isn’t the best basis on which to plead risk socialization and rate uniformity. (More on that point soon!)